Other
Scientific paper
Sep 1995
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1995metic..30q.580s&link_type=abstract
Meteoritics, vol. 30, no. 5, page 580
Other
Isotopes, Osmium, Meteorites, Iron, Rhenium-Osmium Ages
Scientific paper
IVB meteorites. The samples show a limited variation in 187Re/188Os - from 0.3231 (Cape of Good Hope) to 0.3994 (Warburton Range). Consequently, they define an isochron with comparatively low precision: slope=0.07921+/-105; age=4.58+/-0.06 Ga (relative to the IIA and IIIA ages reported previously [1]); initial 187Os/188Os=0.09530+/-37 (MSWD=1.9). The age and initial are unresolvable from isochrons for IIA and IIIA groups[1]. These IVB irons cover the entire range of Ir concentrations in this group, so the limited variation in Re/Os likely reflects the maximum range in IVB, and additional whole-rock data will not likely improve isochron precision. IVA meteorites. Seven IVA irons define an isochron with: slope=0.07721+/-46; age=4.467+/-0.027 Ga; initial 187Os/188Os=0.09584+/-41 (MSWD=1.6). The age is distinctly younger than the ages of the IIA and IIIA groups[1]. Scott et al.[2] show that the parent IVA body probably experienced a catastrophic impact soon after formation, potentially complicating the interpretation of isotopic data. The concentrations of Re and Os, however, are consistent with fractional crystallization, and are quite distinct from possible mixing lines. This likely indicates that that Re-Os systematics were produced via crystal-liquid processes and not by the mixing of native metal with metal from a projectile. The IVA isochron, along with IIA and IIIA isochrons, defines an Os isotope evolution line with slope corresponding to a Re/Os of 0.42, which is identical within error limits to that of H-chondrites. This also argues in favor of an interpretation of the IVA result as a crystallization age. Three additional IVA samples, however, deviate significantly from the isochron - La Grange (+7 sigma), Bushman Land (+7 sigma), and Duel Hill (+15 sigma). According to Scott et al.[2], the latter meteorite does not fit to their IVA crystallization model in most elemental plots. The pronounced deviation in Re-Os system may imply that Duel Hill (1854) does not belong to the main crystallization sequence of the IVA parent body. La Grange and Bushman Land are compositionally consistent with the other IVA irons. They plot within error of the older isochron defined by IIIA irons. Re-Os constraints on crystallization models for magmatic iron meteorites. Re and Os abundance data obtained for IIA, IIIA, and IVA meteorites indicate that parent melts for these groups had chondritic concentrations of refractory siderophiles. In contrast, IVB meteorites are derived from a precursor with distinctly non-chondritic composition. The initial IVB melt had concentrations of Re and Os at least 10 times higher and Re/Os ratio distinctly lower than that of ordinary chondrites [3]. This may imply that IVB precursor material condensed from the solar nebula at much higher temperatures. Figure 1. Re-Os isochron for IVA meteorites. The inset shows data in epsilon-units calculated relatively to the IIA isochron. Samples used for isochron are shown as circles. References: [1]Smoliar M. I. et al. (1995) LPS XXVI, 1323. [2]Scott E. R. D. et al. (1995) GCA, submitted. [3]Walker R. J. et al. (1993) LPS XXIV, 1477.
Smoliar Michael I.
Walker Ray J.
No associations
LandOfFree
Re-Os Study of Magmatic Iron Meteorites with Low GA Abundances--Groups IVA and IVB does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Re-Os Study of Magmatic Iron Meteorites with Low GA Abundances--Groups IVA and IVB, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Re-Os Study of Magmatic Iron Meteorites with Low GA Abundances--Groups IVA and IVB will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-830293